George W. Bush, son of the US President George Bush, playfully steps upon his father 27 January 1990 while he warms up for a run at Fort McNaire Army base while his mother Barbara (R) and US Secret Service agents look on. AFP PHOTO KEVIN LARKIN (Photo credit should read KEVIN LARKIN/AFP/Getty Images)

US President George W. Bush (R) walks alongside his father, former US President George H.W. Bush (L), after arriving on Marine One at the US Naval Observatory in Washington, DC, on March 23, 2008. Bush spent the Easter weekend at Camp David. AFP PHOTO/Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

Former U.S. Presidents George Bush and Bill Clinton speak in the FOX Braodcast booth during the XXXIX Superbowl pregame show at Alltel Stadium on February 6, 2005 in Jacksonville, Florida. (Photo by Frank Micelotta/Getty Images)

George Herbert Walker Bush is pictured when he was one and a half year old. Born 12 June 1924 in Milton, Massachussetts, George Bush yale graduated with a degree in Economics in 1948, made a fortune drilling oil before entering politics in 1964. (FILM) (Photo credit should read AFP/AFP/Getty Images)

George W. Bush (C) poses with father George Bush and his mother Barbara Bush in Rye, New York, summer 1955. George W. Bush is currently campaigning for the Republican party for the presidential election in November 2000. (Photo by Newsmakers)

arbara Bush and George Bush pose with children Neil Bush, George W. Bush, Jeb Bush and Marvin Bush in 1956. George W. Bush is currently campaigning for the Republican party for the presidencial election in November 2000. (Photo by Newsmakers)

George Herbert Walker Bush poses with his wife Barbara during his campaign for Congress in the 1960's. Born 12 June 1924 in Milton, Massachussetts, George Bush Yale graduated with a degree in Economics in 1948, made a fortune drilling oil before entering politics in 1964. (Photo credit should read AFP/AFP/Getty Images)

COLLEGE STATION, TX - JUNE 13: Former U.S. President George H.W. Bush (C, bottom) performs a tandem parachute jump with Army Golden Knight Sgt. Bryan Schnell on June 13, 2004 over the Bush Presidential Library in College Station, Texas. Bush made two jumps today to celebrate his 80th birthday. (Photo by U.S. Army/Texas A&M University via Getty Images)

Former US president George H.W. Bush (R) puts his hand on the shoulder of his son US President George W. Bush as they make their way to board Marine One May 11, 2008 upon arrival at Andrews Air Force Base in Maryland. US President George W. Bush and his family were returning to Washington, DC after attending the wedding of his daughter Jenna at his Crawford, Texas ranch. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

U.S. President Barack Obama (L) presents former U.S. President George H.W. Bush with the 2010 Medal of Freedom in the East Room of the White House February 15, 2011 in Washington, DC. Obama presented the medal to twelve pioneers in sports, labor, politics and arts. (Photo by Chip Somodevilla/Getty Images)

Former President George H. W. Bush (R) and first lady Barbara Bush (C) shake hands with His Excellency the Deputy Prime Minister of the State of Kuwait Sheikh Dr. Mohammad Sabah Al-Salim Al-Sabah after a panel discussion at an event honoring the 20th anniversary of the Persian Gulf War on January 20, 2011 in College Station Texas. The Gulf War was waged against Iraq from August 1990 to February 1991 during President Bush's administration. (Photo by Ben Sklar/Getty Images)

Former U.S. President George H.W. Bush (L) and former first lady Barbara Bush arrive in the East Room for the unveiling of former President George W. Bush's offical portrait at the White House May 31, 2012 in Washington, DC. Commissioned by the White House Historical Association, the portraits will hang in the White House next to portraits of the other past presidents. (Photo by Chip Somodevilla/Getty Images)

Republican presidential candidate, former Massachusetts Gov. Mitt Romney (L) meets with Former President George H.W. Bush and Barbara Bush at Bush's office on March 29, 2012 in Houston, Texas. Mitt Romney received an endorsement from Former President George H.W. Bush and Barbara Bush during the meeting. (Photo by Tom Pennington/Getty Images)

ARLINGTON, TX - OCTOBER 31: Former President of the United States, George W. Bush, and his father Former President George H.W. Bush wave to the crowd before the Texas Rangers host the San Francisco Giants in Game Four of the 2010 MLB World Series at Rangers Ballpark in Arlington on October 31, 2010 in Arlington, Texas. (Photo by Christian Petersen/Getty Images)

ST. PAUL, MN - SEPTEMBER 02: Former President George H.W. Bush (L) and former first lady Barbara Bush (C) point from their seats on day two of the Republican National Convention (RNC) at the Xcel Energy Center on September 2, 2008 in St. Paul, Minnesota. The GOP will nominate U.S. Sen. John McCain (R-AZ) as the Republican choice for U.S. President on the last day of the convention. (Photo by Justin Sullivan/Getty Images)

US President George W. Bush (L) and his father George H. W. Bush take part in the dedication ceremony of the new US embassy on August 8, 2008 in Beijing. US President George W. Bush on August 8 made a new plea for freedom of expression in China as he prepared to attend the opening ceremony of the 2008 Beijing Olympic Games later in the day. AFP PHOTO / Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)

U.S. President George Bush tours a displaced persons' camp 31 December, 1992 in Mogadishu during his two-day visit to Somalia. Children sang songs and greeted him with flowers at the camp, which is run by UNICEF. (Photo credit should read DAVID AKE/AFP/Getty Images)

NEW YORK - SEPTEMBER 24: Former U.S. President Bill Clinton stands with former U.S. President George H.W. Bush during the opening session of the Clinton Global Initiative (CGI) September 24, 2008 in New York City. President Clinton is hosting the fourth annual meeting of the Clinton Global Initiative (CGI), a gathering of politicians celebrities, philanthropists and business leaders grouped together to discuss pressing global issues. (Photo by Spencer Platt/Getty Images)

HOUSTON (AP) - Former President George H.W. Bush is being treated in the intensive care unit at a Houston hospital after suffering "a series of setbacks," including a stubborn fever, his spokesman said.